High quality antialiased lines with dual sampling pattern

Abstract

Antialiased lines are classified according to their orientation, e.g. as x-major or y-major depending whether the x or y extent of the line is larger. Different subpixel sampling patterns are used for different lines, in accordance with this classification. This permits antialiased rendering to achieve increased visual quality of the line without adding in more sample points.

Description

BACKGROUND AND SUMMARY OF THE INVENTION [0001]The present invention relates to 3D computer graphics, and particularly to rendering of antialiased lines.BACKGROUND: 3D COMPUTER GRAPHICS[0002]One of the driving features in the performance of most single-user computers is computer graphics. This is particularly important in computer games and workstations, but is generally very important across the personal computer market.[0003]For some years the most critical area of graphics development has been in three-dimensional (“3D”) graphics. The peculiar demands of 3D graphics are driven by the need to present a realistic view, on a computer monitor, of a three-dimensional scene. The pattern written onto the two-dimensional screen must therefore be derived from the three-dimensional geometries in such a way that the user can easily “see” the three-dimensional scene (as if the screen were merely a window into a real three-dimensional scene). This requires extensive computation to obtain the c...

AI Technical Summary

Benefits of technology

[0010]One common problem, inherent in a raster display system, is that of jagged or “aliased” edges. Aliasing is especially disconcerting at the edges of texture maps. Antialiasing or minimizing the appearance of jagged edges is important to implement in order to avoid this distraction. The effect is accomplished by reducing the contrast between the edge of an object and the color behind it by adjusting pixel values at the edge. This is often done by computing “subpixel” locations, within the area of a single pixel, so that the color values for pixels which overlap an edge are modified in approximate dependence on how much of the pixel falls on either side of the edge.

[0012]The present application describes a new technique for rendering antialiased lines. Lines are classified according to their orientation; for example, in the presently preferred embodiment lines are classified as x-major or y-major depending whether the x or y extent of the line is larger. Different subpixel sampling patterns are used for different lines, in accordance with this classification. This leads to increased visual quality of the line without adding in more sample points.

Problems solved by technology

Some observations contrasting this architecture to earlier ones of 3Dlabs:The message stream does not visit every unit.Trying to route a linear message stream though the texture pipes is fairly problematic, although fanning it out like in Gamma 3 would have been an option.It turns out that the texture units in the texture pipe have little or no state or any need for the color and coordinate information, but are heavily pipelined or have deep latency FIFOs.

If the message stream were increased in width to give the required bandwidth then the cost would be borne in a number of places.

These escape calls are relatively expensive so work is normally packaged up into large amounts before being given to the graphics system.

This can result in the graphics system being idle while work has accumulated in the DMA buffer, but not enough to cause it to be dispatched, to the obvious detriment of performance.

Images